Conference Name: Biomedical Engineering Society (BMES) Annual Meeting 2010
Conventional frequency domain analysis of heart rate variability (HRV) in vivo uses tachograms computed as interbeat interval vs. beat number. Inferences drawn from this analysis are flawed since it ignores the effects of non-uniform sampling. We compared the conventional technique (interbeat interval vs. beat number, CT) to a novel technique (interbeat interval vs. time of occurrence of beat, NT) for the frequency domain analysis of HRV. Guinea pig hearts (n=6) were perfused at a constant pressure of 55 mmHg with Kreb’s-Ringers (KR, 37oC) solution. After 30 min baseline (BL) stabilization, hearts were subjected to 30 min global ischemia and 120 min reperfusion (REP). Bipolar electrograms were recorded from the right ventricle for 4 min each at BL, and after 0 min (REP00), 60 min (REP60), and 120 min (REP120) of REP. Tachograms were computed using CT and NT. For CT the estimated sampling frequency (fs) = 1 Hz and for NT tachograms were interpolated to fs = 40 Hz. We computed: a) total power (TP, 0.04-0.4 Hz for CT and 0.12-16 Hz for NT), b) ratio of power in low frequency (0.04-0.15 Hz for CT and 1.6 to 6 Hz for NT) to high frequency (0.15-0.4 for CT and 6 to 16 Hz for NT) (LF/HF). Results showed: i) during REP00, TP increased more with NT than CT, ii) LF/HF showed no change after REP with CT. Conversely, as noted in vivo, LF/HF decreased after REP with NT. In conclusion, frequency domain analysis of HRV using NT, and not CT, were comparable to in vivo results emphasizing the need to correct for errors due to nonuniform sampling when analyzing HRV in the frequency domain.
N. Nadvar1, B. E. Dunne1, J. Heisner2, A. K. Camara2, D. F. Stowe2, and S. S. Rhodes1,2
1Grand Valley State University, Grand Rapids, Michigan, 2Medical College of Wisconsin, Milwaukee, Wisconsin